> > I repeat my fundamental point: Marx offers no basis for departing > > from Ricardo in defining value in terms of average rather than > > marginal SNLT. I suggest there is no legitimate basis: as I've shown > > by example using Marx's own "pure" case of commodity circulation, > > the condition is essentially self-contradictory.

Duncan writes:

> This could be explained if Marx was thinking of the commodity as an > average of the whole society, as I tend to think he was. This > interpretation would support the idea that Marx did not see the theory of > value as a theory of prices or competition, and therefore the marginal > ideas that arise from that point of view would seem irrelevant to him.

This might be an acceptable interpretation if Marx hadn't
made the case of price-value equivalence the foundation of his
value-theoretic account of capitalist exploitation. But in Chapter 5 of Volume I
he repeatedly refers to the case in which all commodities exchange at their
respective values as the "pure form" of commodity exchange ( a characterization
we now know to be fundamentally problematic), and concludes that this case is
the necessary point of departure in explaining surplus value.

Unfortunately, should this "pure" form of commodity exchange hold,
his definition of value is generally self-contradictory if there are
non-reproducible differences in input quality, for reasons I've
discussed previously.

To put it in other words, one might grant Duncan's point yet insist that
Marx was trying to make his value theory accomplish more than it could.
If that is the case, and if as a consequence we reject completely
the notion that the case of price-value equivalence has anything to do
with anything (as I believe we must), the argument in Volume I, Part 2 must be
completely rewritten, as I've argued elsewhere.